1. Field of the Invention
The present invention relates to laminated ceramic electronic parts and more specifically to laminated ceramic electronic parts such as a laminated ceramic capacitor and a laminated varistor having a structure in which a plurality of internal electrodes are disposed so as to overlap each other via ceramic layers within a ceramic element composing the electronic part.
2. Description of Related Art
A typical laminated ceramic electronic part in the form of a surface mounted laminated ceramic capacitor is shown in FIG. 2. Capacitor 23 is constructed by disposing a pair of external terminals 24a and 24b, which are in electrical contact with a plurality of internal electrodes 22, at opposite ends of a ceramic dielectric block 21. The dielectric block 21 is formed of a lamination of thin ceramic layers 21a having the internal electrodes 22 disposed therebetween. This laminated structure makes it possible to obtain a large capacitance even though the overall size of the capacitor 22 is small.
Due to improvements in the ability to decrease the thickness of the ceramic layers 21a, it has become possible to both reduce the thickness of the ceramic layers 21a and increase the total number of internal electrodes 21a while at the same time decreasing the overall size of the capacitor 23 (or other laminated ceramic electronic part). Laminated ceramic parts having over 100 laminated ceramic layers, each as thin as 5 .mu.m, have become commercially available.
While the reduction in the size of the laminated layers has improved the characteristics of the final product (reduced size and capacitance), it has created manufacturing problems. As a result of the thinning of the ceramic layers, there is little difference between the thickness of the ceramic layers and the thickness of the internal electrodes and the ratio of the combined thickness of the internal electrodes to the total thickness of the electronic part can exceed 3.0. Because the internal electrodes have become a larger percentage of the overall electronic part, they have a much greater effect on the sintering characteristics of the product.
This has the disadvantageous effect of increasing the incidence of delamination and cracking during the sintering process, thus increasing the occurrence of defective parts and degrading the reliability of the parts. Additionally, the laminated ceramic electronic part is likely to form cracks when it receives thermal shocks.